//import java.util.Scanner;
//public class Test6 {
//    public static void main(String[] args) {
//        Scanner scanner = new Scanner(System.in);
//        int n = scanner.nextInt(); // 可以修改n的值来测试不同的情况
//        double percentage = calculatePercentage(n);
//        System.out.println("粉玫瑰占地面积占整个玫瑰花圃总面积的百分比为：" + percentage + "%");
//    }
//
//    public static double calculatePercentage(int n) {
//        int totalArea = n * n;
//        int pinkRoseArea = (n - 2) * (n - 2);
//        return (double) pinkRoseArea / totalArea * 100;
//    }
//}

import java.util.Scanner;
public class Test6 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        double percentage = 1.0 * (4 + n * 2 - 1) / (n * n) * 100;
        System.out.format("%.1f%%", percentage);
    }
}

